1. Field of the Invention
The present invention relates to novel compounds having antagonism against three endothelin isopeptides (endothelin-1, endothelin-2 and endothelin-3), which are physiologically highly active endogenous peptides, processes for their preparation and their use as a drug, and 2-cyanotryptophan or a protected compound thereof which is a key intermediate for preparing the above-mentioned novel endothelin antagonistic compounds.
2. Discussion of Background
Two endothelin receptor subtypes ET.sub.A and ET.sub.B are known so far. The compounds of the present invention possess high affinity to at least the ET.sub.B receptors, thereby inhibiting vasoconstriction and bronchoconstriction induced by the endothelins. The compounds of the present invention provide a new therapeutic potential, particularly for the treatment of hypertension, pulmonary hypertension, Raynaud's disease, acute renal failure, myocardial infarction, angina pectoris, cerebral infarction, cerebral vasospasm, arteriosclerosis, asthma, gastric ulcer, diabetes, endotoxin shock, endotoxin-induced multiple organ failure or disseminated intravascular coagulation, and/or cyclosporin-induced renal failure or hypertension.
Endothelin is a polypeptide composed of 21 amino acids, and it is produced by vascular endothelial cells of human or pig. Endothelin has a potent vasoconstrictor effect and a sustained and potent pressor action (Nature, 332, 411-415 (1988)).
Three endothelin isopeptides (endothelin-1, endothelin-2 and endothelin-3), which resemble one another in structure, exist in the bodies of animals including human, and these peptides have vasoconstriction and pressor effects (Proc. Natl. Acad, Sci, U.S.A., 86, 2863-2867 (1989)).
As reported, the endothelin levels are clearly elevated in the blood of patients with essential hypertension, acute myocardial infarction, pulmonary hypertension, Raynaud's disease, diabetes or atherosclerosis, or in the washing fluids of the respiratory tract or the blood of patients with asthmaticus as compared with normal levels (Japan, J. Hypertension, 12, 79, (1989), J. Vascular Medicine Biology, 2, 207 (1990), Diabetologia, 33, 306-310 (1990), J. Am. Med. Association, 264, 2868 (1990), and The Lancet, ii, 747-748 (1989) and ii, 1144-1147 (1990)).
Further, an increased sensitivity of the cerebral blood vessel to endothelin in an experimental model of cerebral vasospasm (Japan. Soc. Cereb. Blood Flow & Metabol., 1, 73 (1989)), an improved renal function by the endothelin antibody in an acute renal failure model (J. Clin, Invest., 83, 1762-1767 (1989), and inhibition of gastric ulcer development with an endothelin antibody in a gastric ulcer model (Extract of Japanese Society of Experimental Gastric Ulcer, 50 (1991)) have been reported. Therefore, endothelin is assumed to be one of mediators causing acute renal failure or cerebral vasospasm following subarachnoid hemorrhage.
Further, endothelin is secreted not only by endothelial cells but also by tracheal epithelial cells or from kidney cells (FEBS Letters, 255, 129-132 (1989), and FEBS Letters, 249, 42-46 (1989)).
Endothelin was also found to control the release of physiologically active endogenous substances such as renin, atrial natriuretic peptide, endothelium-derived relaxing factor (EDRF), thromboxane A2, prostacyclin, noradrenaline, angiotensin II and substance P (Biochem. Biophys, Res. Commun., 157, 1164-1168 (1988); Biochem. Biophys, Res. Commun., 155, 167-172 (1989); Proc. Natl. Acad. Sci. U.S.A., 85, 9797-9800 (1989); J. Cardiovasc. Pharmacol., 13, S89-S92 (1989); Japan. J. Hypertension, 12, 76 (1989) and Neuroscience Letters, 102, 179-184 (1989)). Further, endothelin causes contraction of the smooth muscle of gastrointestinal tract and the uterine smooth muscle (FEBS Letters, 247, 337-340 (1989); Eur. J. Pharmacol., 154, 227-228 (1988); and Biochem. Biophys. Res. Commun., 159, 317-323 (1989)). Further, endothelin was found to promote proliferation of rat vascular smooth muscle cells, suggesting a possible relevance to the arterial hypertrophy (Atherosclerosis, 78, 225-228 (1989)). Furthermore, since the endothelin receptors are present in a high density not only in the peripheral tissues but also in the central nervous system, and the cerebral administration of endothelin induces a behavioral change in animals, endothelin is likely to play an important role for controlling nervous functions (Neuroscience Letters, 97, 276-279 (1989)). Particularly, endothelin is suggested to be one of mediators for pain (Life Sciences, 49, PL61-PL65 (1991)).
On the other hand, endotoxin is one of potential candidates to promote the release of endothelin. Remarkable elevation of the endothelin levels in the blood or in the culture supernatant of endothelial cells was observed when endotoxin was exogenously administered to animals or added to the culture endothelial cells, respectively. These findings suggest that endothelin is one of important mediators for endotoxin-induced diseases (Biochem. Biophys. Res. Commun., 161, 1220-1227 (1989); and Acta Physiol. Scand., 137, 317-318 (1989)). Further, it was reported that cyclosporin remarkably increased endothelin secretion in the renal cell culture (LLC-PK1 cells) (Eur. J. Pharmacol., 180, 191-192 (1990)). Further, dosing of cyclosporin to rats reduced the glomerular filtration rate and increased the blood pressure in association with a remarkable increase in the circulating endothelin level. This cyclosporin-induced renal failure can be suppressed by the administration of endothelin antibody (Kidney Int., 37, 1487-1491 (1990)). Thus, it is assumed that endothelin is significantly involved in the pathogenesis of the cyclosporin-induced diseases.
Such various effects of endothelin are caused by the binding of endothelin to endothelin receptors widely distributed in many tissues (Am. J. Physiol., 256, R.sup.8 56-R.sup.8 66 (1989)).
It is known that vasoconstriction by the endothelins is caused via at least two subtypes of endothelin receptors (J. Cardiovasc. Pharmacol., 17(Suppl.7), S119-S121 (1991)). One of endothelin receptors is ET.sub.A receptor selective to ET-1 rather than ET-3, and the other is ET.sub.B receptor equally active to ET-1 and ET-3. These receptor proteins are reported to be different from each other (Nature, 348, 730-735 (1990)).
These two subtypes of endothelin receptors are differently distributed in tissues. It is known that the ET.sub.A receptor is present mainly in cardiovascular tissues, whereas the ET.sub.B receptor is widely distributed in various tissues such as brain, kidney, lung, heart and vascular tissues.
Substances which specifically inhibit the binding of endothelin to the endothelin receptors are believed to antagonize various pharmacological activities of endothelin and to be useful as a drug in a wide field. The present inventors already disclosed potent endothelin ET.sub.A receptor antagonists in EP 0460679A2 and EP 0436189A1. Since, the action of the endothelins is caused via not only the ET.sub.A receptor but also the ET.sub.B receptor, novel substances with ET.sub.B receptor antagonistic activity are desired to block activities of the endothelins in various diseases.
Endothelin is an endogenous substance which directly or indirectly (by controlling liberation of various endogenous substances) induces sustained contraction of vascular or non-vascular smooth muscles, and its excess production or excess secretion is believed to be one of pathogeneses for hypertension, pulmonary hypertension, Raynaud's disease, bronchial asthma, gastric ulcer, diabetes, arteriosclerosis, acute renal failure, myocardial infarction, angina pectoris, cerebral vasospasm and cerebral infarction. Further, it is suggested that endothelin serves as an important mediator involved in disease such as endotoxin shock, endotoxin-induced multiple organ failure or disseminated intravascular coagulation, and/or cyclosporin-induced renal failure or hypertension. Two endothelin receptors ET.sub.A and ET.sub.B are known so far. An antagonistic agent against the ET.sub.B receptor as well as the ET.sub.A receptor is useful as a drug. Accordingly, it is an object of the present invention to provide a novel therapeutics for the treatment of the above-mentioned various diseases by an invention of a potent ET.sub.B receptor antagonist.
In order to accomplish the above object, the present inventors have synthesized various peptide derivatives and have investigated their endothelin antagonistic activities, and as a result have found that novel peptide derivatives represented by the following formula (I) and their pharmaceutically acceptable salts have strong potent ET.sub.B receptor antagonistic activities. The present invention has been accomplished on the basis of this discovery.
Thus, the present invention provides a peptide derivative of the formula: ##STR2## wherein R.sup.2 is a hydrogen atom or a lower alkyl group; R.sup.3 is a lower alkyl group which is unsubstituted or substituted with a lower alkylthio group, a lower alkenyl group, a cycloalkyl group or a cycloalkyl lower alkyl group wherein optional one to four hydrogen atoms on the ring may independently be replaced by a lower alkyl group, an aryl group, a heteroaryl group, an aryl lower alkyl group or a heteroaryl lower alkyl group; R.sup.4 is a hydrogen atom, a lower alkyl group or an acyl group; X and Y are mutually dependent; when X is a group of the formula R.sup.11 --O--C(.dbd.O) or a group of the formula R.sup.12 R.sup.13 N--C(.dbd.O), Y is a group of the formula: ##STR3## wherein R.sup.11 is a lower alkyl group or an aryl group, R.sup.12 is a lower alkyl group, a cycloalkyl group, a cycloalkyl lower alkyl group, a 1-adamantyl group, or an aryl group or a heteroaryl group wherein optional one or two hydrogen atoms on the ring may independently be replaced by an optional group selected from the group consisting of a lower alkyl group, a lower alkoxy group, a halogen atom, a trifluoromethyl group, a nitro group, an amino group and a formyl amino group, R.sup.13 is a hydrogen atom, a lower alkyl group which is unsubstituted or substituted with a hydroxyl group, a cycloalkyl group or a cycloalkyl lower alkyl group, or R.sup.12 and R.sup.13 form, together with the adjacent nitrogen atom, a 5- to 9-membered nitrogen-containing saturated heterocyclic ring having 4 to 8 carbon atoms (wherein among methylene groups forming the ring, optional one methylene group may be replaced by a thio group, optional one to four hydrogen atoms on the carbon atoms of the heterocyclic ring may independently be replaced by a lower alkyl group or a hydroxy lower alkyl group, and further two adjacent carbon atoms in the heterocyclic ring may form a benzo-fused ring), R.sup.5 is a hydrogen atom, or a lower alkyl group or a lower alkenyl group which may have one to three substituents selected from the group consisting of a hydroxyl group, a lower alkoxy group, a lower alkylthio group, an aryl group and a heteroaryl group, n is 0 or 1, Z is a hydroxymethyl group, a group of the formula CO.sub.2 R.sup.61 (wherein R.sup.61 is a hydrogen atom or a lower alkyl group ), a group of the formula CONR.sup.62 R.sup.63 (wherein each of R.sup.62 and R.sup.63 is independently a hydrogen atom, an aryl group, a heteroaryl group, or a lower alkyl group which may have one to three substituents selected from the group consisting of a hydroxyl group, a carboxyl group and a sulfo group), a 1H-tetrazol-5-yl group, a sulfo group or a phosphono group, and when X is a group of the formula: ##STR4## , Y is a group of the formula: ##STR5## wherein R.sup.71 is a hydrogen atom, R.sup.72 is a lower alkyl group which is unsubstituted or substituted with a lower alkylthio group, a cycloalkyl group, an aryl group or a heteroaryl group, or R.sup.71 and R.sup.72 together form an alkylene group having 2 to 5 carbon atoms, m is 0, 1 or 2, Q is a group of the formula COOR.sup.8 (wherein R.sup.8 is a hydrogen atom or a lower alkyl group), a sulfo group or a 1H-tetrazol-5-yl group, each of R.sup.91 and R.sup.92 is independently a hydrogen atom, or a lower alkyl group or a lower alkenyl group which may have one to three substituents selected from the group consisting of a hydroxyl group, a lower alkoxy group, a mercapto group, a lower alkylthio group, a carboxyl group, a carbamoyl group, an amino group, a guanidino group, an aryl group and a heteroaryl group, or R.sup.91 and R.sup.92 together form an alkylene group having from 2 to 4 carbon atoms wherein optional one hydrogen atom in the alkylene group may be replaced by a hydroxyl group, and one sulfur atom may be present, and U and W together form a single bond; or a pharmaceutically acceptable salt thereof.
In addition, the present invention provides a 2-cyanotryptophan or a protected compound thereof of the formula: ##STR6## wherein P.sup.1 is a hydrogen atom or an amino-protecting group, P.sup.2 is a hydrogen atom or a carboxyl-protecting group, and P.sup.3 is a hydrogen atom or an indolyl-protecting group, which is a key intermediate for preparing the above-mentioned peptide derivatives.
Now, the present invention will be described in further detail with reference to the preferred embodiments.
Now, the meanings of various abbreviations used in this specification will be given.
______________________________________ Abbreviation Meaning of Abbreviation ______________________________________ Ile L-isoleucine Leu L-leucine .gamma.MeLeu .gamma.-methyl-L-leucine DNle D-norleucine DNva D-norvaline DTrp D-tryptophan Boc tert-butoxycarbonyl Me methyl .sup.t Bu tert-butyl Bzl benzyl Cpeg L-cyclopentylglycine CDI 1,1'-carbonyldiimidazole DCC N,N'-dicyclohexylcarbodiimide DMAP 4-(dimethylamino)pyridine DMF N,N-dimethylformamide DMSO dimethylsulfoxide NMM N-methylmorpholine EDCI.HCl 1-ethyl-3-(3-dimethylamino- propyl)carbodiimide.hydro- chloride HOBT.H.sub.2 O 1-hydroxy-1H-benzotriazole mono- hydrate TEA triethylamine TFA trifluoro acetic acid THF tetrahydrofuran TsOH p-toluene sulfonic acid MOPS 3-morpholinopropane sulfonic acid HEPES 2-[4-(2-hydroxyethyl)-1- piperazinyl]ethane sulfonic acid Tris tris(hydroxymethyl)aminomethane PMSF phenylmethanesulfonyl=fluoride DAsp D-aspartic acid DtertLeu D-2-amino-3,3-dimethylbutanoic acid DPen D-penicillamine DPen(Me) S-methyl-D-penicillamine Pip L-pipecolinic acid Pro L-proline DTrp(2-Cl) 2-chloro-D-tryptophan DTrp(2-Br) 2-bromo-D-tryptophan DTrp(1-Boc, 2-Cl) 1-tert-butoxycarbonyl-2- chloro-D-tryptophan DTrp(1-Boc, 2-Br) 1-tert-butoxycarbonyl-2- bromo-D-tryptophan DTrp(1-Boc, 2-CN) 1-tert-butoxycarbonyl-2- cyano-D-tryptophan DTrp(2-CN) 2-cyano-D-tryptophan Val L-valine Fmoc 9-fluorenylmethoxycarbonyl Pac phenacyl Pfp pentafluorophenyl DIPC N,N'-diisopropylcarbodiimide EDT 1,2-etanedithiol Pd/C palladium on activated carbon ______________________________________
Now, the definitions of the various terms mentioned in this specification will be explained.
In this specification, the lower alkyl group means a straight or branched chain hydrocarbon group having 1 to 6 carbon atoms such as a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 1-methylbutyl, 2-methylbutyl, 1,2-dimethylpropyl, 1-ethylpropyl, hexyl, isohexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 2,2-dimethylbutyl, 1-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-2-methylpropyl or 1-ethyl-1-methylpropyl group.
The cycloalkyl group may, for example, be a cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl or cyclononyl group.
The cycloalkyl lower alkyl group means an alkyl group having 1 to 6 carbon atoms which is substituted with a cycloalkyl group having 3 to 6 carbon atoms such as a cyclopropylmethyl, 1-cyclopropylethyl, 2-cyclopropylethyl, 1-cyclopropylpropyl, 2-cyclopropylpropyl, 3-cyclopropylpropyl, cyclopentylmethyl, 2-cyclopentylethyl, cyclohexylmethyl, 2-cyclohexylethyl, 2-cyclohexylpropyl group.
The aryl group may, for example, be a phenyl, 1-naphthyl or 2-naphthyl group.
The aryl lower alkyl group means a lower alkyl group which is substituted with an aryl group defined above such as a benzyl, 2-phenylethyl, 3-phenylpropyl, 5-phenylpentyl, 6-phenylhexyl, 1-phenylethyl, 1-naphthylmethyl, 2-(1-naphthyl)ethyl, 3-(1-naphthyl)propyl group.
The heteroaryl group means a heterocyclic or fused heterocyclic group containing at least one hetero atom such as an oxygen, nitrogen or sulfur atom, for example, a thienyl, furyl, thiazolyl, imidazolyl, pyridyl, indolyl or benzothienyl group.
The heteroaryl lower alkyl group means a lower alkyl group which is substituted with a heteroaryl group defined above such as a 2-thienylmethyl, 2-(2-thienyl)ethyl, 3-(2-thienyl)propyl, 2-furylmethyl, 2-(2-furyl)ethyl, 2-thiazolylmethyl, 4-imidazolylmethyl, 2-(4-imidazolyl)ethyl, 3-(4-imidazolyl)propyl, 2-pyridylmethyl, 2-(2-pyridyl)ethyl, 3-indolylmethyl, 3-benzothienylmethyl group.
The lower alkenyl group means a straight or branched chain hydrocarbon group of 2 to 6 carbon atoms having at least one double bond such as a vinyl, allyl, 2-propenyl, isopropenyl, 3-butenyl, 2-butenyl, 1-butenyl, 1-methyl-2-propenyl, 1-methyl-1-propenyl, 1-ethyl-1-ethenyl, 2-methyl-2-propenyl, 2-methyl-1-propenyl or 4-pentenyl group.
The alkylene group means a straight chain bridge of 1 to 6 carbon atoms connected by single bonds such as a methylene, ethylene or propylene group.
The lower alkoxy group means a straight or branched chain alkoxy group having 1 to 6 carbon atoms such as a methoxy, ethoxy, propoxy or isopropoxy group.
The halogen atom means a fluorine, chlorine, bromine or iodine atom.
The lower alkylthio group means a straight or branched chain alkylthio group having 1 to 6 carbon atoms such as a methylthio, ethylthio, propylthio, isopropylthio group.
The acyl group means a group derived from organic acids by deletion of an OH group such as a formyl, acetyl, propionyl, benzoyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, phenoxycarbonyl, N-methylcarbamoyl, N-ethylcarbamoyl, N,N-dimethylcarbamoyl, methylsulfonyl, ethylsulfonyl, phenylsulfonyl, dimethylphosphoryl or diethylphosphoryl group.
The amino-protecting group means a urethane type protecting group such as a t-butoxycarbonyl, benzyloxycarbonyl, p-methoxybenzyloxycarbonyl or 9-fluorenylmethoxycarbonyl group, an acyl type protecting group such as a formyl, trifluoroacetyl or tosyl group, or an alkyl type protecting group such as a trityl group.
The carboxyl-protecting group means a group which forms an ester such as a methyl, ethyl, t-butyl, benzyl or phenacyl ester.
The indolyl-protecting group may, for example, be a formyl, t-butoxycarbonyl, benzyloxycarbonyl or benzenesulfonyl group.
Now, this invention will be described in more detail with reference to specific examples for the various symbols used in the formula (I) and (V).
R.sup.2 means a hydrogen atom or a lower alkyl group. Examples of the lower alkyl group are methyl and ethyl groups.
R.sup.3 means a lower alkyl group which is unsubstituted or substituted with a lower alkylthio group, a lower alkenyl group, a cycloalkyl group or a cycloalkyl lower alkyl group wherein optional one to four hydrogen atoms on the ring may independently be replaced by a lower alkyl group, an aryl group, a heteroaryl group, an aryl lower alkyl group or a heteroaryl lower alkyl group. Examples of the lower alkyl group which is unsubstituted or substituted with a lower alkylthio group are methyl, ethyl, methylthioethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and tert-pentyl groups. Examples of the lower alkenyl group are vinyl, allyl, 2-propenyl, isopropenyl, 3-butenyl, 2-butenyl, 1-butenyl, 1-methyl-2-propenyl, 1-methyl-1-propenyl, 1-ethyl-1-ethenyl, 2-methyl-2-propenyl, 2-methyl-1-propenyl and 4-pentenyl groups. Examples of the cycloalkyl group or the cycloalkyl lower alkyl group wherein optional one to four hydrogen atoms on the ring may independently be replaced by a lower alkyl group are cyclopropyl, 2-methylcyclopropyl, 2-ethylcyclopropyl, 2-propylcyclopropyl, 2,2-dimethylcyclopropyl, 2,3-dimethylcyclopropyl, 2,2,3,3-tetramethylcyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 2-methylcyclopropylmethyl, 2-ethylcyclopropylmethyl, 2-propylcyclopropylmethyl, 2,2-dimethylcyclopropylmethyl, 2,3-dimethylcyclopropylmethyl, 2,2,3,3-tetramethylcyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl, cyclohexylmethyl, 1-cyclopropylethyl, 2-cyclopropylethyl, 1-cyclopropyl-1-methylethyl, 1-cyclobutylethyl, 2-cyclobutylethyl, 1-cyclobutyl-1-methylethyl, 1-cyclopentylethyl, 2-cyclopentylethyl, 1-cyclopentyl-1-methylethyl, 1-cyclohexylethyl, 1-cyclohexyl-1-methylethyl, 1-cycloheptylethyl and 1-cyclooctylethyl groups. Examples of the aryl group are phenyl and 1-naphthyl groups. Examples of the heteroaryl group are 2-thienyl, 2-thiazolyl and 2-furyl groups. Examples of the aryl lower alkyl group are benzyl and 2-phenylethyl groups. Examples of the heteroaryl lower alkyl group are 2-thienylmethyl, 2-(2-thienyl)ethyl, 2-thiazolylmethyl, 2-furylmethyl, 2-pyridylmethyl, 3-indolylmehtyl and 3-benzothienylmethyl groups.
R.sup.4 means a hydrogen atom, a lower alkyl group or an acyl group. Examples of the lower alkyl group are methyl and ethyl groups. Examples of the acyl group are formyl, acetyl, propionyl, benzoyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, phenoxycarbonyl, N-methylcarbamoyl, N-ethylcarbamoyl, N,N-dimethylcarbamoyl, methylsulfonyl, ethylsulfonyl, phenylsulfonyl, dimethylphosphoryl and diethylphosphoryl groups.
In X, R.sup.11 means a lower alkyl group or an aryl group. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethylbutyl, 1-ethyl-1-methylpropyl and 1,1,2-trimethylpropyl groups. Examples of the aryl group are phenyl, 1-naphthyl and 2-naphthyl groups.
In X, R.sup.12 means a lower alkyl group, a cycloalkyl group, a cycloalkyl lower alkyl group, a 1-adamantyl group, an aryl group or a heteroaryl group wherein 1 or 2 optional hydrogen atoms on the ring may be replaced by an optional group selected from the group consisting of a lower alkyl group, a lower alkoxy group, a halogen atom, a trifluoromethyl group, a nitro group, an amino group and a formylamino group. Otherwise, R.sup.12 and R.sup.13 may form, together with the adjacent nitrogen atom, a heterocyclic group as indicated below. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethylbutyl, 1-ethyl-1-methylpropyl and 1,1,2-trimethylpropyl groups. Examples of the cycloalkyl group are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl groups. Examples of the cycloalkyl lower alkyl group are cyclopropylmethyl, 1-cyclopropylethyl, 2-cyclopropylethyl, 1-cyclopropylpropyl, 2-cyclopropylpropyl, 3-cyclopropylpropyl, cyclopentylmethyl, 2-cyclopentylethyl, cyclohexylmethyl, 2-cyclohexylethyl, 3-cyclohexylpropyl groups. Examples of the aryl group or a heteroaryl group wherein 1 or 2 optional hydrogen atoms on the ring may be replaced by an optional group selected from the group consisting of a lower alkyl group, a lower alkoxy group, a halogen atom, a trifluoromethyl group, a nitro group, an amino group and a formylamino group, are phenyl, 2-fluorophenyl, 2-chlorophenyl, 2-bromophenyl, 3-fluorophenyl, 3-chlorophenyl, 3-bromophenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 2,6-difluorophenyl, 2,6-dichlorophenyl, 2,6-dibromophenyl, 2-aminophenyl, 2-formylaminophenyl, 2-trifluoromethylphenyl, 2-nitrophenyl, 3-aminophenyl, 3-formylaminophenyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-thienyl and 3-thienyl groups.
In X, R.sup.13 means a hydrogen atom, a lower alkyl group which is unsubstituted or substituted with a hydroxyl group, a cycloalkyl group or a cycloaokyl lower alkyl group. Otherwise, R.sup.13 and R.sup.12 may form, together with the adjacent nitrogen atom, a heterocyclic group as indicated below. Examples of the lower alkyl group which is unsubstituted or substituted with a hydroxyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hydroxymethyl, 2-hydroxyethyl and 3-hydroxy propyl groups. Examples of the cycloalkyl group are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl groups. Examples of the cycloalkyl lower alkyl group are cyclopropylmethyl, 1-cyclopropylethyl, 2-cyclopropylethyl, 1-cyclopropylpropyl, 2-cyclopropylpropyl, 3-cyclopropylpropyl, cyclopentylmethyl, 2-cyclopentylethyl, cyclohexylmethyl, 2-cyclohexylethyl, 3-cyclohexylpropyl groups.
In X, R.sup.12 and R.sup.13 may also form, together with the adjacent nitrogen atom, a 5- to 9-membered nitrogen-containing saturated heterocyclic group having 4 to 8 carbon atoms. Among methylene groups forming the heterocycle, one optional methylene group not adjacent to the above nitrogen atom may be replaced by a thio group, and one to four optional hydrogen atoms on the carbon atoms of the heterocycle may independently be replaced by a lower alkyl group or a hydroxy lower alkyl group, and further two adjacent carbon atoms in the heterocycle may form a fused-benzene ring. Examples of the heterocyclic group are pyrrolidino, piperidino, perhydroazepin-1-yl, perhydroazocin-1-yl, perhydroazonin-1-yl, 1,3-thiazolidin-1-yl, indolin-1-yl, isoindolin-2-yl, 3-pyrolin-1-yl, 1,5-dihydro-2H-pyrrol-1-yl, perhydro-1,4-thiadin-4-yl, 1,2,3,4-tetrahydroquinolin-1-yl, 1,2,3,4-tetrahydroisoquinolin-2-yl, 1,2,3,4-tetrahydropyridin-1-yl, 1,2,3,6-tetrahydropyridin-1-yl, perhydro-1,4-thiazepin-4-yl, 2,3,4,5-tetrahydro-1-benzazepin-1-yl, 2,3,4,5-tetrahydro-2-benzazepin-2-yl, 1,2,4,5-tetrahydro-3-benzazepin-3-yl, 2,3,4,5-tetrahydro-lH-azepin-1-yl, 2,3,6,7-tetrahydro-1H-azepin-1-yl, 1,3,4,7-tetrahydro-2H-azepin-1-yl, perhydro-1,4-thiazocin-4-yl, 1,2,3,4,5,6-hexahydro-1-benzazocin-1-yl, 1,2,3,4,5,6-hexahydro-2-benzazocin-2-yl, 1,2,3,4,5,6-hexahydro-3-benzazocin-3-yl, 1,2,3,4,5,6-hexahydroazocin-1-yl, 1,2,3,4,7,8-hexahydroazocin-1-yl and 1,2,3,4,5,8-hexahydroazocin-1-yl groups, or the above-mentioned heterocyclic groups wherein one to four optional hydrogen atoms on the carbon atoms of the heterocycle may independently be replaced by a lower alkyl group or a hydroxy lower alkyl group. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl groups. Examples of the hydroxy lower alkyl group are hydroxymethyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl, 3-hydroxybutyl and 4-hydroxybutyl groups.
In Y, R.sup.5 means a hydrogen atom, or a lower alkyl or lower alkenyl group which may have 1 to 3 substituents selected from the group consisting of hydroxyl, lower alkoxy, lower alkylthio, aryl and heteroaryl groups. Examples of the lower alkyl or lower alkenyl group which may be substituted by 1 to 3 substituents selected from the group consisting of hydroxyl, lower alkoxy, lower alkylthio, aryl and heteroaryl groups, are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, hydroxymethyl, 1-hydroxyethyl, methoxymethyl, 1-methoxyethyl, methylthiomethyl, ethylthiomethyl, propylthiomethyl, butylthiomethyl, 2-methylthioethyl, 2-ethylthioethyl, 3-indolylmethyl, 4-imidazolylmethyl, vinyl, allyl, 2-propenyl, isopropenyl, 3-butenyl, 2-butenyl, 1-butenyl, 1-methyl-2-propenyl, 1-methyl-1-propenyl, 1-ethyl-1-ethenyl, 2-methyl-2-propenyl, 2-methyl-1-propenyl, 4-pentenyl, 1-hydroxy-2-propenyl, 1-methoxy-2-propenyl, 1-methylthio-2-propenyl, 2-hydroxy-3-butenyl and 2-ethylthio-3-butenyl groups.
In Y, Z means a hydroxymethyl group, a group of the formula CO.sub.2 R.sup.61, a group of the formula CONR.sup.62 R.sup.63, a 1H-tetrazole-5-yl group, a sulfo group or a phosphono group.
In Z, R.sup.61 means a hydrogen atom or a lower alkyl group. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and hexyl groups.
In Z, each of R.sup.62 and R.sup.63 means independently a hydrogen atom, an aryl group, a heteroaryl group or a lower alkyl group which may have 1 to 3 substituents selected from the group consisting of a hydroxyl group, a carboxyl group and a sulfo group. Examples of the aryl group are phenyl 1-naphthyl and 2-naphthyl groups. Examples of the heteroaryl group are 2-thienyl, 3-thienyl, 2-furyl and 3-furyl groups. Examples of the lower alkyl group which may have 1 to 3 substituents selected from the group consisting of a hydroxyl group, a carboxyl group and a sulfo group, are methyl, ethyl, propyl, 2-hydroxyethyl, carboxymethyl, 1-carboxyethyl, 2-carboxyethyl, sulfomethyl and 2-sulfoethyl groups.
In X, R.sup.71 means a hydrogen atom. Otherwise, R.sup.71 and R.sup.72 may form an alkylene group having 2 to 5 carbon atoms.
In X, R.sup.72 means a lower alkyl group which is unsubstituted or substituted with a lower alkylthio group, a cycloalkyl group, an aryl group or a heteroaryl group. Otherwise, R.sup.72 and R.sup.71 may form an alkylene group having 2 to 5 carbon atoms. Example of the lower alkyl group which is unsubstituted or substituted with a lower alkylthio group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, methylthiomethyl, 1-methylthioethyl, 2-methylthioethyl, 1-methyl-1-methylthioethyl, 1-methyl-1-methylthiopropyl, 1-methyl-1-ethylthioethyl and 1-methyl-1-propylthioethyl groups.
In X, R.sup.71 and R.sup.72 may also form an alkylene group having 2 to 5 carbon atoms. Example of the alkylene group having 2 to 5 carbon atoms are groups of the formula --(CH.sub.2).sub.2 --, --(CH.sub.2).sub.3 --, --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.5 --.
In X and Y, U and W form, together with each other, a single bond.
In Y, m means 0, 1 or 2.
In Y, Q means a group of the formula COOR.sup.8, a sulfo group or a 1H-tetrazol-5-yl group. In Q, R.sup.8 means a hydrogen atom or a lower alkyl group. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and hexyl groups.
In Y, each of R.sup.91 and R.sup.92 means independently a hydrogen atom, a lower alkyl group or a lower alkenyl group which may have 1 to 3 substituents selected from the group consisting of a hydroxy group, a lower alkoxy group, a mercapto group, a lower alkylthio group, a carboxyl group, a carbamoyl group, an amino group, a guanidino group, an aryl group and a heteroaryl group. Otherwise, R.sup.91 and R.sup.92 may form, together with each other, an alkylene group having 2 to 4 carbon atoms wherein optional one hydrogen atom in the alkylene group may be replaced by a hydroxyl group, and further one sulfur atom may be present. Examples of the lower alkyl group or the lower alkenyl group which may have 1 to 3 substituents selected from the group consisting of a hydroxyl group, a lower alkoxy group, a mercapto group, a lower alkylthio group, a carboxyl group, a carbamoyl group, an amino group, a guanidino group, an aryl group and a heteroaryl group, are hydroxymethyl, mercaptomethyl, carbamoylmethyl, 2-carbamoylethyl, carboxymethyl, 2-carboxyethyl, 4-aminobutyl, 3-guanidinopropyl, 4-imidazolylmethyl, 3-indolylmethyl, phenylmethyl and (4-hydroxyphenyl)methyl groups. Examples of the alkylene group having 2 to 4 carbon atoms wherein optional one hydrogen atom in the alkylene group may be replaced by a hydroxyl group, and further one sulfur atom may be present, are groups of the formula --(CH.sub.2).sub.2 --, --(CH.sub.2).sub.3 --, --(CH.sub.2).sub.4 --, --CH.sub.2 --S--CH.sub.2 -- and --CH.sub.2 --CH(OH)--CH.sub.2 --.
P.sup.1 means a hydrogen atom or an amino-protecting group. Examples of the amino-protecting group are t-butoxycarbonyl, benzyloxycarbonyl, p-methoxybenzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trifluoroacetyl, tosyl and trityl groups.
P.sup.2 means a hydrogen atom or a carboxyl-protecting group. Examples of the carboxyl-protecting group are groups which form methyl, ethyl, t-butyl, benzyl and phenacyl esters.
P.sup.3 means a hydrogen atom or an indolyl-protecting group. Examples of the indolyl-protecting group are formyl, t-butoxycarbonyl, benzyloxycarbonyl and benzenesulfonyl groups.
Now, the process for producing the novel peptide derivatives, and 2-cyanotryptophan and a protected compound thereof of the present invention will be described.
A 2-cyanotryptophan or a protected compound thereof of formula (V) of the present invention may be produced by reacting a compound of formula (VI): ##STR7## wherein P.sup.4 is an amino-protecting group, P.sup.5 is a carboxyl-protecting group, P.sup.6 is an indolyl-protecting group, and L is a leaving group, with a cyanide such as copper(I) cyanide, sodium cyanide or potassium cyanide in the presence of, if necessary, copper salt such as copper(I) iodide or copper in an inert solvent such as N,N-dimethylformamide, dimethylsulfoxide or pyridine at room temperature to the boiling point of the solvent, preferably at 50.degree. C. to 120.degree. C., for 10 min to 24 h, preferably for 30 min to 8 h, followed by, if necessary, deprotection of the protecting group(s) and protection of functional group(s). Racemization of the .alpha.-position of the tryptophan derivative can be avoided during the reaction of the compound of formula (VI) with a cyanide, the deprotection and the protection procedures. Therefore, each D-form, DL-form or L-form of the compound of formula (V) is obtained from each D-form, DL-form or L-form of the compound of formula (VI), respectively.
Examples of the amino-protecting group described by P.sup.4 are t-butoxycarbonyl, benzyloxycarbonyl, p-methoxybenzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trifluoroacetyl, tosyl and trityl groups.
Examples of the carboxyl-protecting group described by P.sup.5 are groups which form methyl, ethyl, t-butyl, benzyl and phenacyl esters.
Examples of the indolyl-protecting group described by P.sup.6 are t-butoxycarbonyl, benzyloxycarbonyl and benzenesulfonyl groups.
Examples of the leaving group described by L are chlorine, bromine and iodine atoms, and methanesulfonyl, trifluoromethanesulfonyl and toluenesulfonyl groups.
A peptide derivative of formula (I) of the present invention can be prepared using a 2-cyanotryptophan or a protected compound thereof of formula (V) as a starting material by a method wherein amino acids composing the target peptide derivative are condensed one by one, by a method wherein condensation products of plural amino acids are condensed with each other, or by a combination of such methods, and further, if a peptide derivative of formula (I) is a cyclic pentapeptide, by cyclizing the corresponding linear pentapeptide wherein the side-chain functional groups of the amino acid residues may be protected as the case requires, and then, if necessary, removing a C-terminal protective group or side-chain protective groups.
Condensation can be conducted in a liquid phase or in a solid phase according to known methods such as a DCC method, an azide method, an active ester method and a mixed acid anhydride method (described, for example, by M. Bodansky and M. A. Ondetti in Peptide Synthesis, Interscience, New York, 1966; by F. M. Finn and K. Hofmann in The Proteins, Vol. 2, ed. by H. Nenrath and R. L. Hill, Academic Press Inc., New York, 1976; by Nobuo Izumiya et al. in Peptide Synthesis, Maruzen, 1975).
As a starting material of the peptide derivative of the present invention, both D- and DL-form of a 2-cyanotryptophan or a protected compound thereof can be used, however, the D-form is preferable.